Fixes for various SB related retain issues (please review)

Investigating SB issues, turns out that an empty timeline will still always play the default timeline and then perform the sequenceComplete selector. (Not sure if it needs to but always has so leaving it alone).
CCActionCallFun retains this.

CCActionCallFunc set target node to weak,
Setup scheduler in CCAnimationManager only if added to a node (onEnter)

spritebuilder/SpriteBuilder#638
spritebuilder/SpriteBuilder#653
spritebuilder/SpriteBuilder#654